Forehearth for molten glass



Jan. 3, 1933. K. E. PEigER FOREHEARTH FOR MOLTEN GLASS Filed Sept. 19,1929 8 sheets-shea 1 Jama 3 1933. K. E. PEaLER FOREHEARTH FOR MOLTENGLASS Filed Sept. 19, 1929 8 Sheets-Sheet 2 l /la Jan. 3, 1933.

K. E. PEILER 1,893,061

FOREHEARTH FOR MOLTEN GLASS Filed Sept. 19, 1929 8 Sheets-Sheet 3 WZ'Z ness.

Jan. 3, 1933. K. E. PEILER FOREHEARTH FOR MOLTEN GLASS 1929 8Sheets-Sheet 4 Filed Sept Z/mm WM I Jan 3y 1933 K. E. PEiLER 39893,@62

FOREHEARTH FOR MOLTEN GLASS Filed Sept, 19, 1929 8 Sheets-Sheet 5 8Sheets-Sheet 6 K. E. PEILER FOREHEARTH FOR MOLTEN GLASS Filed Sept. 19,1929 Jan. 3, 1933.

8 sheets-sheet 7 ZZe, 16445104/ V7) [fi 77E Pe K. E. PEiLER 'FOREHEARTHFOR MOLTEN GLASS Filed sept. 19, 1929 Jan. 3, 1933.

Jan. 3, 1933.

K. E. PEzLER 1,893,061

FOREHEARTH FOR MOLTEN GLASS Filed Sept. 19, 1929 8 Sheets-Sheet 8/f'l/Ql i Y/Ziz a' e2@ in Wiz@ s /faHZZT Pfz'ie;

f e5 Lf? i tra, a, ieee E. EEHIER, OF WEST HARTFORD, CONNEGTCUT,ASSIGNOR T0 HARTFORD-MEME COMPANY F HARTFORD, (ZNNEGTKCUT, il QEPORTONOlq1 DELAWARE lFGBmE-ETH FR MGMT@ GLASS application neu september ie,reas. serial no. scacco.

rlhis invention relates to improvements in orehearths lor receivingmolten glass from a melting furnace and tor conducting such vglass to a`leed spout, basin, or other supply chamber from which glass is to beted, gath- V ered, drawn or otherwise removed.

lit is usual in taking glass from a melting furnace or tanlr to providea orehearth or extension, having a channel along which molten glass 'ows:trom the furnace or tank to a place at which glass is to be `ed in moldchargess gathered by suction in a gathering receptacle, or otherwiseremoved. Glass dov/ing along a channel oit a :torehearth or extensiontends to lag or dow more slowly and to become relatively cool at thesides ot the channel While hotter glass will flow at a relatively highvelocity along the longitudinal median portion ci@ the channel, thusproducing the condition known as channeling. rlhis condition isobjectionable in that the glass entering the chamber or place oi?delivery or removal ot glass at the outer end ot the orehearth oreirtension is notuniiorrn in viscosity, tempera-- ture and condition. lnsome instances, the relatively cool and stagnant glass at the sides otthe *forehearth channel may become cordy or partially devitriiied andportions thereof may be entrained `Witli the relatively hot and moreswiftly ilovving glass at 'the longitudinal :media-n portion el thetorehearth and may seriously interfere with the feeding or removal otglass at the delivery end of the torehearth.

lt has been proposed prior to the present invention to eliiect coolingof the glass at the longitudinal median portion of the forehearthchannel with a view to reducing the temperature and velocity ot ovv otsuch glass to coincide more nearly `with the temperature and velocity offlow of glass at the side portions of the orehearth channel. Patent No.l,656,869, granted to ine January l?, 1928, illustrates and disclosesmeans for and methods orn cooling the glass at the longitudinal medianportion ot the tank by providing an opening or openings in the top otthe -torehearth above thelongitudinal median portion thereof andregulating the effective size and character of such' opening or openingsto etlect regulable accelerated cooling of the glass at the middle or"the 'forehearth channel. 'lhe construction and methods of such patentobviate many of the 'objectionable teatures' of orehearths providedprior thereto. However, the opening or openings at the top of theorehearth tend to influence draft and ring conditions Within theorehearth and, in some circumstances, it may be desirable to obviatesuch influence on draft and ring conditions.

lt also has been proposed to etllect local cooling of part of the glassin a 'orehearth by passing a cooling medium through a member adjacent tosuch glass. ln some instances, the member through which the coolingmedium is to be passed is a refractory Wall of the glass conductingchannel. Such local cooling, it etiective to lower the tem.

perature and reduce the velocity or ovv oi" any portion of glass in theforehearth, probably also would tend to lower the temperature and rateot' iloW of the remaining glass in the torehearth and thus might preventthe delivery at the outer end of the orehearth of glass at adesirablyhigh temperature. Moreover, such local cooling of relativelyhot glass in the iiorehearth Would not obviate the objectionablefeatures which result jfrom the presence of the cooler and more slowlymoving or stagnant glass at the sides o the torehearth.

An object ot the present invention is to provide for the conditioning ofglass during its passage along the flow channel of a forehearth or lilreextension Arorn a melting 'furnace or other source of supply oi moltenglass to a leed spout, gathering basin or other place of delivery otglass at the outer end of the torehearth so that the glass passing tosuch place of delivery will be or uniform temperature, viscosity andcondition throughout and ci proper temperature5 viscosity and conditiontor use in the manner desired.

further object of the invention is to produce an even tloW ofi the glassin the channel o a forehearth throughout the cross section oix suchglass by causing a relatively greater radiation or heat from the glassat the longitudinal median portion ofi torelll@ hearth without causingany interference with or influence on the draft and firing conditionswithin the forehearth and by distributing the temperature within thespace above the glass in the forehearth so that the heating of the glassin the side portions of the channel of the forehearth will beintensified as required to produce a. condition of uniform viscosit andtemperature throughout the' cross section of the glass in the channel.

A further object of the invention is the provision of improved means forand improved method of cooling glass in the longitudinal median portionof a forehearth by radiation alone while preventing drafts or iow ofcold air at the cooling place. v

y A further object of the invention -is to provide improved means forcausing independently regulable flow of heating media longitudinally ofthe forehearth above the glass in the side portions ofthe glass fiowchannel.

l above the glass in the furnace is practically prevented by closingcommunication between the space above the glass in the forehearth andthe space above the glass in the furnace. Conditioning and control oftheA temperature and viscosity of the glass in the forehearth areeffected by regulating` the temperature and' draft conditions in theforehearth to control the distribution transversely of the forehearth ofthe currents of heating media `which move longitudinally of theforehearth above the glass therein, as by causing the heated gases topass lon itudinally of the forehearth mainly or entirely at the sideportions thereof, and by causing relatively greater radia, tion of heatfrom the glass at the longitudinal medium portion -ofV the forehearthwithout opening the space above such glass to the atmosphereand-therefore without influencing or altering' draft or firinglconditions in the forehearth.

A desirable arrangement for effecting conditioning of glass in theforehearth and distribution of heat therein comprises a source of heat,such as a burner, located so as to discharge a heating blast downwardlyand forwardly into the outer end portion of the forehearth and means,such as stacks having dampers therein, in communication with the rear.or inner portion-.of the space above the glass in the forehearth atopposite sides of the longitudinal median line thereof for in.

ducing drafts rearwardly igthe forehearth above the.k glassanfthe .sideportions of the glass conducting 1 channel of the forehearth whereby theheating of the glass in the side portions o'f the forehearth will berelatively great. VIn conjunction with this local heating of the glassin the side portions of the forehearth, the invention` provides forregulably ycontrolled relatively great radiation of heat y 'the frontorl outer end portion of the forehearth and the velocity and heatingcharacteristics of the heating media passing. rearwardly above the glassin the side portions of the forehearth may be regulated by regulatingthe intensity` and volume of flame from the burner and/or regulating thedraft inducing action of the stacksat the rear of the forehearth. j

In the drawings:

Figure 1 is a. `generallyA longitudnal vertical sec-tion through'aforehearth embodying the invention and shown appurtenant to a portion ofal glass melting tank, the section line on which the view is takenextending centrally of 4the forehearth from the outer end of theforehearth for part of the length thereof and then. being offsetlaterally to extend nearerito one side ofthe forehearth for theremainder ofthe length of the latter;

Fig. 2is a transverse vertical section to the forehearth, substantiallyalong the line 2--2 of Fig. 1;

Fig. 3 is a .fragmentary vertical section through. a portion of the topof the forehearth embodying the invention, showing -a removablerefractory block in position to reduce or prevent heat radiation from aportion of the heat rad'ating metallic cover section of the top of theforehearth; p

Fig. 4 is a view similar to Fig. 3 but showing a modified form of topstructure of a forehearth embodying the invention and illustrating'amethod of preventing radiation of heat through part or all of themetallic cover plate of the top by placing a removable refractory blockor blocks beneath part or, all of such metallic cover plate.

Fi g. 5`is a fragmentary longitudinal vertical section through avmodified forehearth structure, generally similar tothat shown in Fig. 1but provided at its outer end with a gathering basinand means forregulating the draft conditions therover; y

' Fig. 6 is a view similar .to Fig. 1 but showing a forehearth having abasin for a gathering pool at its outer/end and provided with a modifiedformof heat radiation controlling 'neeaeei top structure and with amodified construction for controlling the transverse distribution ofheat within the space above the glass in the forchearth;

Fig. 7 is a transverse section through the forehearth structure of Fig.6, taken substantially along the line 7 7 of Fig. 6; Y

Fig. 8 is a fragmentary longitudinal vertical section through aforehearth generally similarto that shown in Fig. 6 but provided at itsouter end with a spout for the feeding of glassY through a submergedoutlet;

Fig. 9 is aview generally similar to Fig. 1 but showing another form offorehearth structure embodying the invention;

Fig. 10 is a transverse section through the forehearth structure of Fig.9, the view being taken substantially along the line 10-16 of Fig. 9;

Fig. 11 is a fragmentary longitudinal vertical section through stillanother form of forehearth embodying the invention;

Fig. 12 is a transverse vertical section 'along the line 12-12 of Fig..11;

Fig. 13 is a view similar to Fig. 11, showing still another formofforehearth structure for carrying out the invention;

Fig. 14 is a fragmentary plan view, partly in section, showing a portionof the forev` hearth vstructure of Fig. 13'; and

Fig. 15 is a transverse vertical section substantially along the line15-15 of Fig. 13.

rlhe forehearth structure shown in Figs. 1 and 2 comprises a metallicframe work 1 connected with the frame structure of a melting tank 2,Fig. 1, so as to permit independent expansion and contraction of thewalls of the forehearth and of the 'melting furnace. The glassconducting channel of the forehearth is supported by the metallic framestructure and comprises a refractory bottom, side and top wallsrespectively indicated generally at 3,- 4 and 5. The walls of theforehearth channel are Aspaced from the metallic frame work structure bysuitable refractory spacingmembers, such as indicated at 6 and adjustingmechanism, such as those indicated at 7, whereby the forehearth channelwill be supported bv the metallic casing and may be adjusted relativelythereto according to particular requirements or conditions and asrequired to receive molten glass 8 from the furnace outlet 9 to the bestadvantage. rll`he refractory glass conducting walls of the forehearthchannel may be insulated, as by insulation such as indicated at 10, atthe bottom, sides and for part of the top thereof to prevent orminimizeradiation of heat from the glass through such portions of the fore- 601hearth. A suitabl insulated refractory feed spout 11 is provi ed at theouter end of the glass conducting channel, Fig. 1.k rlhis lfeed spout isshown as having a discharge outlet 12 in its base, below the glasslevel, through 65 which molten glass may be discharged under the controlof the glass feeding mechanism generally indicated at 13.

A refractory separator block 14 extends transversely of the glass`conducting channel adjacent to the furnace outlet and dips into theglass so as to prevent communication between the space above the glassin thefurnace 'and the space above the glass in the forehearth.

The structure shown is suitable for the feeding of glass in mold chargesand as described so far is generally similar in' con'- struction to thatof the forehearth structure of the well-known Hartford single feeder, adisclosure of which may be found in my copending application, Serial No.683,57 6, filed December 31, 1923.

A pair of stacks 15 communicate with the space above the glass at theinner or rear portion of the forehearth at opposite sides of thelongitudinal median line of the forehearth channel. Each of these stacksis provided with a damper 16 and with suitable mechanism 17 foradjusting the damper to vary the effective draft outlet of the stack.

The space above the glass adjacent to the feed spout 11 is enlargedupwardly to provide a firing chamber 18. rlhe walls of the firingchamber 18 are formed of suitable refractory material and. so far aspracticable, preferably are provided on their outer surfaces with heatinsulating material. The rear wall of such firing chamber preferably isinclined forwardly and upwardly and constitutes a burner block.indicated at 19, provided with an inwardly enlarging opening 2() throughwhich flame from a burner 21 may be projected forwardly and downwardlyin the firing chamber. rlhe top wall of the ring chamber preferably isinclined downwardly and forwardly, as indicated at 22, so that the flameand heat from the burner 21 will be deflected downwardly and forwardlyinto the feed spout and against the glass therein. the inner walls ofthe feed spout being formed to cause a return or rearward movement ofthe heated gases close to the glass in the forehearth channel.

With this arrangement, the llame and heat from the burner not only willlocally heat the glass passing into the feed spout and in the latter butwill be constrained to pass rear-` wardly along the surface of the glassin opposte side portions of the forehearth ch annel to the stacks 15 andthence through the latter to the atmosphere. The effective heatingaction and velocity of movement of the heated gases above the glass in4the side portions of the forehearth channel may be regulated byadjusting the dampers 16, by controlling the volume and character offlame from the burner 21, or by a combination of these adjustments. As aresult of the passage of the heated gases above the glass in the sideportions of the forehearth channel, the glass which otherwise would tendto become colder and-more viscous and to How more slowly than the glassat the longitudinal median portion of the forehearth channel is heatedmore intensely than the middle glass, thus tending to cause more uniformvelocity of flow and temperature and viscosity conditions in the glassthroughout the cross section of the glass conducting channel.

In addition to the control of the distribution of heat transversely ofthe forehearth, a further control of the temperature and viscosityconditions throughout the cross section of the forehearth is effected bymeans which will now be described. The longitudinal median portion ofthe refractory top 5 of the glass conducting channel of theforehearth iscut away, as indicated at 23, to provide an opening of predeterminedlength and width above the glass 'at the longitudinal median line of theforehearth. A metallic cover plate 24 is arranged tocover theopening123. The cover plate 24 preferably is an arched member, as shown,having supporting flanges at.

its marginal edges insulated from the refractory top wall of the'forehearth' by suitable heat insulating material, such as indicated-at,25. This metallic cover plate 24 should have high heat resistingqualities. A

metal known commercially as Q-alloy has been found to be satisfactoryfor the purpose. The insulation on the refractory top of the glassconducting channel of the forehearth may extend flush with the crown ofthe cover member 24, las shown in Figs. 1 and 2.

- A cooling pipe 26 for blowing air or other i cooling media on' themetallic member 24 may be disposed above the latter and may be providedwith longitudinally spaced downwardly turned discharge nozzles 27, eachprovided with an independently controllable valve 28,' whereby themember 24 may be locally cooled to dilferent extents at different placesalong its length.

The operation of the embodiment of the invention just described may besubstantially as follows:

Molten glass from the tank 2 will flow through the tank outlet 9 beneaththe refractory separator or gate member 14 into the flow channel of theforehearth. Tendency of the glass in the side portions of the flowchannel to lag behind the glass in the longitudinal median portion ofthe flow channel and to become cooler and more viscous may beminimizedor practically prevented by reason of the relatively intenseand greater local heating ofthe glass in the side portions of theorehearth by the heated gases which are conducted in clearly definedchannels from the firing` chamber 18 rearwardly along the side walls ofthe forehearth .channel to the stacks 15.` At the same time, thetemperature of the glass at thek longitudinal median portion of theforehearth channel may be reduced by -claimed in my copending reason ofthe relatively greater radiation heat through the metallic heatradiating plate section of the glass at the forward end ofthe channelmay be obtained. The glass supplied to the feed spout 11 therefore willbe homogeneous and of uniform and desirable telnperature, viscosity andcondition.

It may be desirable at times to shut oil' the relatively greaterradiation of heat fron the longitudinal median portion of the forehearththrough the metallic plate 24 or through a portion thereof. This may bedone by placingl a refractory block 29 on lthe me' tallic member 24 oron any portion of the latter, as shown in Fig. 3. If desired, theinetallic coolino' member may extend above the heat insulation on therefractory top 5a of the forehearth channel, as illustrated in F ig.4,-in which the metallic cooling member 1s designated generally atA24a'. 1n such construction, the metallic cover member may includehinged side sections 30, each of which may be swung outwardly andupwardly to permit a refractory cover block 31 to bev essential respectswith the construction of Fig. 1 as hereinbefore described except thatthe feed spout 11 and associate feeding mechanism 13 o f theconstruction of Fig. 1 are replaced in the construction of Fig. 5 by abasin 38 for holding'a pool of moten glass from which glass mayberemoved by suction molds or`other gathering receptacles. The iring'spaceof the construction shown in Fig. 5 is indicated'at 18a and the frontwall thereof may comprise a vertically adjustable refractory baille 39which depends close to the glass and is adjustable to Vary the exchangeof heat permitted between the space in the firing chamber and the spaceabove the glass in the gathering basin. Suitable glass circulatingmeans, not shown, may be provided for use in connection with the glassgathering pool in the basin 38. The basin construction of the form o fforehearth shown in Fig. 5 comprises features which are disclosed and.prior application, Serial No. 387 ,285, filed August 21` 1929, and whichtherefore need not Y as they are not being claimed in this application.The same reference: characters have been usel to designate like parts ofthe conbe described herein structions of Figs. 1 and 5 and the operationof the construction shown in Fig. 5 will be y understood fromthehereinbefore given statement of the operation of the construction ofFig. 1 supplemented by the brief description above given of theconstruction of Fig. 5.

In the construction shown in Figs. 6 and 7, the refractory top 56 of theforehearth channel comprises blocks which extend transversely acrosssuch channel and have central por-` tions thereof depending downwardlyto provide a longitudmal baille 32. The ytop 5a is formed with a seriesof longitudinally spaced openings 33, each of which may be formed in oneof the component blocks of the top 5a. Each opening 33 extendsdownwardly through the baffle portion 32 of the refractory top of thechannel and is covered at its upper end by a metallic heat radiatingcover member 34. An individual blow nozzle 35, provided with aregulating valve 36, may be provided above each of the cove-r plates 34for projecting a regulable volume of air or other cooling media againstthe plate 34. The baffie 32 depends close enough to the glass levelpractically to prevent passage of any appreciable volume of heated gasesalong the lonitudinal median portion of the glass in the orehearth andthe side Walls of the baille 32 cooperate with the adjacent portions ofthe side walls 4a of the glass conducting channel of the forehearth andof the refractory top 5a to define passages, indicated at 37, above theside portions of the forehearth channel through which heated gases andproducts of combustion pass from the firing chamber 18a, at the front ofthe' forehearth rearwardly to the stacks 15a. Each of the stacks 15a isprovided with a damper'l and with damper adjusting mechanism 17. Theparticular forehearth structure shown in Fig. 6 has thefront or outerend portion thereof formed as P a basin 38, as in Fig. 5, for holding apool4 of molten glass from which glass may be re i moved by suction inmolds or other gathering receptacles.- In order to controldraft andtemperature conditions over the glass in the gathering basin, the frontor outer wall of the firing chamber 18a may comprise the verticallyadjustable refractory baile 39 which depends close to the glass butcanbe adjusted with respect to the glass level to vary the exchange of heatbetween the space in the firing chamber and the space above the glass inthe gathering basin.

The glass conducting channelof'the rfoehearth construction of Fig. 6 maycorrespond in all other essential respects with the construction shownin Fig. 1 and heretofore de- Y scribed. Consequently parts of-theconstruction of Fig. 6 which are identical or not essentially differentfrom corresponding parts of Fig.r 1 will not be described but aredesignated by the same reference characters as The construction shown inFig. 8 diers 'from that shown in Fig. 6 in that a feed spout 11a andglass feeding mechanism 13 are provided, as in Fig. 1, at the outer endof the forehearth in lieu of the gathering basin 38 of F ig. 6.Otherwise, the construction shown in Fig. 8 conforms in all essentialrespects with the construction shown in Fig. 6.

ln Figs. 9 and 10, the refractory top of the glass conducting channel isdesi nated 56 and may be said to be of the canti ever type ofconstruction. rlfhis top wall comprises longitudinal series ofcantilever blocks having their outer portions supported on the sideWalls 46 of the forehearth channel structure and on portions of the sidemembers of the metallic casing, as best seen in F ig. 10, such blocksbeing clamped securely in place by the metallic side frame members 40,the metallic top plate 41 and `the adjustable connections 42 between themetallic top and side frame members. The cantilever blocks of therefractory top of the glass conducting channel have portions spacedapart above the longitudnal median portion of the forehearth channel toprovide the opening 236. A metallic cover plate 246 covers the openin236 and may be retained in place by thec amp members 43. The cantileverblocks have cutaway portions at their bottoms to provide the centralbaille .326 and the side passa es 44 for conducting heated gases from teA firing chamber 186 ,to the stacks 156. Acooling pipe 266 having theseparate nozzles 276 ar-r spaced portions of the metallic plate lmay beprovided for locally applying cooling air or other cooling mediato thelates 246, if desired. Each of the nozzles 2 6 may be rovided with aseparate re ulating valve 286. The remaining parts oft e constructionshown in Figs. 9 and 10 are substantially identical with .correspondingparts of the construction shown in Fi 1 and have beenl designated by thesame re erence characters.

In Figs. 11 and 12, the refractory top of the forehearth channel isdesignated generally at 5c and is of the arched type of construction.'The component blocks of this arched refractory top member of theforehearth channel are supported on the refractory side walls 4c of thechannel structure, as best seen in Fig. 12, and include crown or keyblocks haying depending lower portions formed to provide a baille 320above the longitudinal median portion of the forehearth channel for partof the length of the latter and the side passages 370 for the v-assageof heated gases 1':

ins

QF lard tion shown in the baile 320, and is covered at its upper end bya heat radiating metallic plate 34e. Anv individual blow nozzle '-350provided with a separate valve 36e may be provided. above each of theplates 340 for discharging air or cooling media thereon. The remainingparts of the forehearth structure of Figs. 1.1 and 12 arenot-essentially different from like parts of the constructiongof Fig. 1and have been designated by the same' reference characters.

The forehearth co struction of Figs. 13 to 15 inclusive has are actorytop designated 5d, comprising refractory blocks so formed and sodisposed as t provide longitudinally spaced vertical openings 33d abovethe longitudinal median portion of the glass in the forehearth and themuffled longitudinally ex tending side passages 37 for conducting heatedgases from thel front firing chamber 18d to the lowerends of the stacks15d. As clearly shown in Fig. 15, the, blocks of 'the refractory top 15dhave their lower surfaces close to the glass level,and the heating ofthe glass in the side portions of the glass conducting channel iseffected by radiant heat imparted from the gases passing through fluesor muilled passages 37d through the bot-- toms of such passages to theglass therebeneath. Each of the openings 33d is covered at its upper endby a metallic heat radiating plate 34d. Such o enings may be square incross-sectional con guration as shown in Fig. 14. A separate blow nozzle35d, controlled by a valve 36d, may be provided above each of themetallic plates 34d, for discharging` air or other cooling mediumthereagainst when desired.

The remainin portions of the construc- Figs. 13`to 15, inclusive, aredesignated by the same reference characters as generally correspondingparts of they c'onstruction'shown in Fig. 1.

In'the use of each of the specifically different constructionshereinbefore described and illustrated in the respective views of thedrawings, conditioning of the glass in the forehearth may be regularlycontrolled by the conjoint action of the means which controls thedistribution of temperature and draft .conditions within the forehearthand the means which permits relatively greater radiation of'heat fromthe glass at the longitudinal medianv portion of the forehearth so thatthe glass passing to a feed spout, glass athering basin or othersupply-chamber at e outer end o the forehearth will be uniform intemperature, viscosity and condition and will be of desiredpredetermined regulable condition, temperature and viscosit for use as'required for a particular service. The regulation and control of thetemperature and condition of the glass within the fore# hearth may beentirely independent of draft and temperature conditions within thespace above tbe glass in-the furnace and is effected 'of said channel.

furnace of a Vforehearth having a channel along which nace, means orintroducin a heating medium into the s ace above tle lass adjacent tothe outer en of the channe and separate v draft inducing meansrespectively communif lass may iow from said fur-,

eating at opposite sides of the longitudinal median line of theforehearth with the space above the glass adjacent to the inner end ofsaid channel for causing the path of movement of heat from the outer endof the channel .to-be mainl above the side portions of the glass insaichannel.

2. Thel combination with a glass melting furnace of a forehearth havin.an enclosed channel along whiclrmolten g ass may flow from the furnace,means for introducing a heating mediuminto the space above the glassadjacent to the outer end of said channel, and a pair of stacksrespectively lcommunicating at opposite sides of the longitudinal medianline of the channel with the'space above the glass adjacent to the innerend of the channel for causing the heated gases at the outer end of thechannel to pass longitudinally of the channel abovethe glass in the sideportions 3. The combination with a glass melting furnace of a forehearthpro'ecting therefrom and havin a flow channel or receivin molten glassrom the furnace, said fore earth having a firing chamber above the glassadjacent to the outer end ofthe channel and having separate draftinducing means respectively in communication at o posite sides of thelongitudinal median line o the channel with the space above the glassadjacent to Athe inner end of the channel, and means for projectin aheating mixture in combustion downwar l'y .and forwardly in said firingchamber abovethe longitudinal median line ofsaid channel. y

l 4.1The combination with a glass melting furnace of a forehearth projectin therefrom and having a channel along whi glass may flow from thefurnace, means for separating the space above the glass in theforehearth from the ace above the glass in theA furnace, means forintroducing a heating medium into ass in said channel adthe space abovethe jacent to one end of tie latter to cause heating of the glass in theforehearth independently of heat from the furnace, means, includingseparate draft Ainducing means, respectively communicating with thespace above the glass in the channel at opposite sides of thelongitudinal median line thereof, for causin the heated gases in theforehearth to trave lon-l rasee-,oei

greater radiation of heat `from glass atthev longitudinal median portionof said channel than from the glass in the side portions ot saidchannel.

5. 'lhe combination with a glass melting furnace of aorehearthprojecting therefrom and having a channel along which glass mayflow from the furnace, means for introducing a heating medium into thespace above the glass adjacent to the outer end of the channel, a coverstructure :for said channel having an imperforate lmetallic portionlocated' above the glass in the longitudinal median portion of saidchannel to cause a relatively greater radiation of heat from part of thelass at the longitudinal median portion'ot t e channel than from theglass in the side portions of the channel, saidmetallic portion havingits outer surface exposed at the top of said cover structure, means torcausing heated gases-Withintheforehearth to travel longitudinally ot thechannel mainly above the glass in the side portions or' said channel andmeans for insulating the glass conducting channel of the Jorehearth atthe bottom and sides thereof.

6.' 'lhe combination with a glass melting furnace of a orehea'rth havinga refractory channel along `which glass may now from the orehearth,means. separating the space above the glass in the orehearth from thespace above the glass in the furnace, means Jfor introducing a'heatin'Vmedium into the space above the glass in t e Jorehearth, means forcontrolling the distribution of flow of heated gases Within theloreheartli to cause said eli) heated ases to travel mainly above theglass in the side portions of said channel, and impertcraf metallicmeans above part oi the glass at the longitudinal medianl portion ofsaid channel for causing a relatively greater radiation or heat' fromthe glass at the longitudinal median portion ot the channel than fromthe glass in the side portions of the dow channel, said impertoratemetallic means having its inner surface exposed to heat from theunderlying glass and its outer surface exposed at the outer side of theorehearth.

7. The combination with a glass melting turnace of a orehearth having arefractory channel along which glass may flow from the furnace, means'separating t ie space above the glass in the forehearth from the spaceabove the glass in the furnace, means tor introducing a heating mediuminto the space above the glass in the orehearth, means tor controllingthe distribution ot iloW of heated gases Within the orehearth to causesaid heated gases to travel mainly above the glass in the side portionsof said channel, imperiorate metallic means above part ot the glass atthe longitudinal median portion of said channel for causing a relativelygreater radiation ci heat from the glass at the longitudinal medianportion o the channel than trom' the glass in the side portions or saidchannel, said impertorate metallic means being in direct heatcommunicating' relation with bot-h the space Within the orehearth andthe atmosphere outside or the orehearth, and means lfor locally coolingsaid imperiorate heat radiating means. l

8.".lhe combination-With a glass melting 'furnace of a orehearth havinga refractory channel along which glass may ow from the orehearth, meansseparating the space above the glass in the orehearth from the spaceabove the glass in the furnace, means Sor introducing a heating mediuminto the space above the glass in the orehearth, meansfor controllingthe distribution ot. new of' heated gases Within the torehearthto causesaid heated gases to travel mainly above the glass in the side portionsci said channel,

imperiorate metallic means above part of the y glass at the longitudinalmedian portion o' said'channel ior causing a relatively greaterradiation of heat from the glass at the lon gitudinal median portion otthe channel than :trom the glass in the side portions ot the channel,and means tor locally cooling said imperforate heat radiating means,said coo-ling means being adjustable to vary the cooling ot saidimperiiorate metallic means inde# pendently at a plurality of ditierentAplaces above the longitudinal median line ci the lorehearth 9. 'lhecombination vvitha glass melting furnace oi" a orehearth projectingtherefrom and having a channel along'vvhich' glass'may flow trom thefurnace, said channelha-ving refractory bottom, side and top Walls, saidrefractory top Wall being spaced from the I` glass in the channel,refractory means scparating the space above the glass in the channel'from the space above the glass in the turnace, said refractory topvvall having a vertical opening iormed therein above the longitudinalmedian line of the channel, ametallic member completelyclosing the uppervend ot' said opening 'to cause a relatively greater radiation oit heatfrom the glass belovv said metallic member than'trom the glass in theside portions ot said channel, means for introducing va heating mediuminto the space above the glass adjacent to one end of said channel, andmeans for controlling the distribution ot llow of heated gases above theglass in the channel to cause said heated gases to travel longitudinallyof the Jforehearth mainly above the glass in the side portions ot saidchannel and laterally of the space beneath said metallic heat radiatingmember.

l0. rl`he combination with a glass melting furnace o a forehearthprojecting therefrom and having a channel along which glass may iiovvfrom the furnace, said channel having refractory bottom, side and topWalls, said 'ies l refractory to wall being spaced from the glass in thec annel, refractory means separating the space above the glass in thechannel from the space above the glass in the furnace, said refractorytop wall having a vertical opening formed therein 'above the longitudi-4nal median line of the channel, a -metallic member completely closingthe upper end of said opening inv the refractoryvtop Wall of thelchannel to cause a relatively greater radiationifofjheat from the glassbelow said me- -tallic member than from 'the glass in the side portionsof said channel, means for introducing a heating mediuminto the spaceabove the glass adjacent to one end of said channel, and means forcontrolling the distribution of flow. of heated gases above'the glass inthe channel to cause said heated gases to travel longitudinally of theforehearth mainly above the glass in the side portions of said4 channelandv laterally of the space beneath said metallic heat radiating member,said heat radiating member being formed'to per-v mit removablerefractory blocks to be placed in position to shut olf said relativelygreat radiation of `heatthrough aregulable portion or all of saidopening in the refractory top member.

11. The combination with a glass melting furnace of aforehearth'projecting therefrom and having anenclosed channel alongwhich glass may owfrom the furnace, said forehearth being formed toprovide side passages above the glass in the side portions of said .35channel for conducting heated gases lo ngi-,l

tudinally of the forehearth, means separating the space above the glassin the forehearth from the space above the glass in thefurnace, ymeansfor introducinga heating medium into 40 the space above the glass in thechannel adjacent to one end of each of said side passages, and separatemeans in communication with the space above the glass in the channel atthe opposite end of each of said side passages for causing a draft ineach side passage, whereby the heated' gases in said channel will travelmainly through said side passages, and imperforate means located abovethe space' between said side passages for causinoa rela- 5. tivelygreater radiation of heat from the glass at thelongitudinal medianportion of the.

channel than from the glass below said side passages. v

12, The combination with a glass meltingv 55 furnace of a forehearthprojecting therefrom and havin a channel along which molten glass may owfrom the furnace, said channel having refractory bottom, side and topwalls, the refractory top wall of the channel having w a verticalopening therein above the longitudinal median line ofthe glass in thechannel, andl an imperforate metallic closure for the upper end of saidopening for causing a relatively greater radiation of heat from glass atthe longitudinal median portion of the channel than from the glass intheside portions of said channel.

1 3. The combination with a glass melting furnace of a forehearthprojectin therefrom and having a channel along whic glass may flow fromthe furnace, said channel having a top structure formed with arelativelyv thin mperforate portion above the `glass in-the longitudinalmedian portion. of the channel to cause a relativeily greater radiationof heat from the longitudinal median portion of the glass in the channelthan from the glass in the side portions of said channel, the inner andouter surfaces of saidimperforate portionLof the top structurerespectively being exposed to heat from the underlying glassand to acooling medium above the forehearth.

14. The combination with a glass meltingl said furnace, means forintroducing a mix` ture, in combustion into a firing space above theglass in the. channel adjacent toone end of the latter, .and separateindependently regulable draft inducing means communicating at oppositesides of the longitudinal median line of the channel top for causingindependently regulable flow of heated gases from said firing spacelongitudinally of the channel above the glass in the side portions ofsaid channel.

15. The combination with a glass melting furnace of a forehea'rth havinga channel along which glass may flow from said fur nace, a coverIenclosing said channel, said cover having a longitudinally-extendingchamber with a bottom opening communicating with the space above thelongitudinal median portion of the glass in the channel, and means forabsorbing heat from said chamber while the top 'of said chamber isclosed to the atmos here.

16. The combination with a glass melting furnace of a forehearth havinga channel along which glass may flow from said furnace, a coverenclosing said channel, chamber means disposed in said cover forproviding a heat column` above the median portion of the glass in thechannel higher ythan the heat column above the side portions of saidchannel and means for. absorbing heat from said chamber while'the top ofsaid chamber is .closed to the atmosphere;

